Power Analyses When Comparing Trimmed Means

Abstract

Given a random sample from each o f two independent groups, this article takes up the problem of estimating power, as
well as a power curve, when comparing 20% trimmed means with a percentile bootstrap method. Many methods were
considered, but only one was found to be satisfactory in terms of obtaining both a point estimate of power as well as a
(one-sided) confidence interval. The method is illustrated with data from a reading study where theory suggests two
groups should differ but nonsignificant results were obtained.